Hydroformylation of propene

ABSTRACT

Described is an improved process for preparing butyric aldehydes by hydroformylation of propene in the presence of cobaltcarbonyls complexed with phosphines. The process is characterized in that a reaction medium is used chosen from among N.N-dialkylamides, tetra-alkyl-ureas, aliphatic nitriles and dinitriniles, containing from two to 12 carbon atoms. The operating temperatures are between 110* and 220* C. and the operating pressures of CO+ H2 are between 20 and 400 atmospheres.

United States Patent [72] Inventors App]. No.

Filed Patented Assignee Gianfranco Pregaglia Milan;

Alberto Andreetta'; Luigi Benzoni, both of Novara, all of Italy Mar. 13,1968 Dec. 14, 1971 Montecatini Edison S.p.A.

Milan, Italy HYDROFORMYLATION OF PROPENE 2 Claims, No Drawings 11.5. CI260/604 HF, 260/632 HF Int. Cl C07c 45/08 Field oi Search 260/604 HF 56]References Cited UNITED STATES PATENTS 3,239,569 3/1966 Slaugh et al.260/604 X 2,834,812 5/1958 Haughes et al. 260/604 2,820,059 II] 958Hasek et al. 260/604 between 20 and 400 atmospheres.

HYDROFORMYLATION F PROPENE Our invention is concerned with thehydroforrnylation of propene. Various processes are known for obtainingC aldehydes by hydroformylation of propene with CO and H, in thepresence of simple of modified cobalt-carbonyls. Under these conditions,isobutyric aldehyde is obtained in addition to the main productn-butyric aldehyde, with the ratio of normal to branched aldehyde:3-4/1. So far no processes for the synthesis of aldehydes with a normalto branched isomer ratio higher than :1 are known.

0x0 products with high linear to branched chain ratios have beenobtained recently (French Pat. No. 1,345,933 to Shell lnter. Res. Mij.)by hydroformylation of propene. However, mixtures of C, aldehydes andalcohols are obtained. The selectivity in C aldehydes is not very highbecause of the pronounced hydrogenating properties of the catalyticsystem used. 0n the other hand, as in the case of hydroforrnylation ofpropene to obtain C, alcohols, it is necessary to stop thehydroformylation at the stage of C aldehyde formation, inasmuch as onlythese can be easily and effectively condensed in order to obtainalcohols with twice the number of carbon atoms. Therefore, thepossibility of high selectivity hydroformylation of propene to n-butyricaldehyde constitutes a considerable advantage in the industrialproduction.

We have surprisingly found out that n-butyric aldehyde can be obtainedin high selectivity by using a suitable reaction solvent. This solventcan be chosen from organic compounds having from two to 12 carbon atomsand containing CN or groups, such as NN-dialkyl-amides,tetra-alkyl-ureas, aliphatic nitriles and dinitriles. In particular,conveniently used solvents are dimethyl-formamide, dimethyl-acetamide,tetra-methylurea, acetonitrile, adipo-nitrile, etc. The C aldehydes,obtained when operating in these solvents, have normal to iso ratioshigher than 5.5/1 and are accompanied by only small quantities ofalcohols. I

The catalysts used are cobalt-carbonyls substituted by Lewis bases,preferably phosphines. Particularly favorable are trialkyphosphines with2-8 C alkyls, e.g. triethylphosphine, trin-butylphosphine, etc.

Examples of cobalt-carbonylic complexes suited for the reaction are:[Co(CO),P(n-C H,),] HCo(CO),[P(n-C H,),. /2- HCO a)s sis, 4 s)a]2' Thecatalyst may be formed in situ" by reacting soluble cobalt salts,phosphine and carbon monoxide. The quantity of catalyst used rangesbetween 5 and 200 milliatoms of cobalt per liter of solvent. Inpractice, concentrations of 60-890 milliatoms of cobalt per liter ofsolvent are preferred.

Temperatures between ll0and 220 C. are operable, but temperatures from160 to 200 C. are preferred. The reaction pressure may vary from to 400atmospheres. In practice, it is preferred to operate at pressurescomprised between 40 and 210 atmospheres and in particular between 90and 120 atmospheres. The gaseous mixture fed contains CO and H, in apreferably molar ratio.

Although the mechanism of this reaction is not at all clear, it ispossible that the solvents used in the present process substantiallymodify the structure of the introduced carbonylic complex. The tablebelow gives the absorption wave numbers in the zone of the carbonyls aswell as the intensities of the [.R. bands of the reaction solution and,for comparison, of other solutions obtained by operating under the sameconditions (see example 3), but with different solvents:

The following examples are given for purposes of illustration only andare not intended to limit the invention.

EXAMPLES l A rocking stainless steel autoclave of 200 cc. capacity,provided with a manometer, was accurately washed with pure nitrogen.Thereupon there were introduced:

Z-ethylhexanoate ofcobllt 1.535 g. (4.45 mM.) tri-n-butyl-pholphine 1.09g. (5.39 mM.) dimethyl-formamlde 60 cc.

propene 6.48 (154.3 mM.)

On attaining 172 C. (pressure 19 atm.) the H CO mixture (l: 1 by volume)was introduced until reaching a total pressure of 45 atmospheres. Theabsorption of the gas started at once. The total pressure was maintainedbetween 45 and 40 atmospheres by feeding in new mixture. Afier 64atmospheres of gas had been absorbed, the reaction was interrupted bycooling down the autoclave.

The gases discharged were carefully measured and gas-volumetricallyanalyzed in order to determine the content of propane and propene. Theliquid was analyzed by gas-chromatography at C, in order to determinethe contents in C, hydrocarbons, C alcohols, C aldehydes and C. alkylformates. An 8 meter column filled with di-isodecylphthalate onChomosorb W(diatomaceous powder of 30-60 mesh of the Johns-ManvilleCorp.) was used for the gas chromatography. The C, compounds weredetermined at C., by means of a 4 meter column filled with Carbowax 1540(polyethyleneglycol of the Applied Science Laboratories lnc.).

The discharged products, liquid and gaseous, contained 76.1 mM. ofpropene, 6.93 mM. of propane, 59.8 mM. of C aldehydes, 8.15 mM. of C,alcohols and 0.28 mM. of C, alkyl fonnates.

EXAMPLE 2 By operating according to the same procedure with the sameamount of reactants as in example 1,but stopping each reaction about at50-55 percent completion, three comparative tests were carried out inthree different reaction mediums. The following table shows thedependence of selectivity of C, aldehydes on the reaction medium used inthe hydroformylation of propane:

lapsed between the introduction of the H CO mixture and the cooling ofthe autoclave. The selectively (column 3) represents the moles of Caldehydes obtained from 100 moles of converted propene. The ratiobetween the linear and branched products (column 5) was calculated onthe sum of alcohols aldehydes.

Since the above tests differ only as to the reaction medium used, thetable just evidences that the higher selectivity obtained in DMF (testof example 1 is'due only to the use of that particular reaction medium.

EXAMPLE 3 A rocking stainless steel autoclave of 200 cc. capacity,provided with a manometer, was carefully washed with pure nitrogen.Thereupon were introduced:

[Co(CO),P(nC,H,) 2.525 g. (3.66 mM.) I'm-(3,11,), 1.785 g. (8.83 mM.)HCO.N(CH.), 100 cc.

propene 10.6 g. (252.4 mM.)

After feeding in the 1-1,-Co (1:1 by volume) mixture until attaining atotal pressure of 68 atmospheres, the autoclave was heated up to 180 C.The absorption of gas started at about 160 C. The-total pressure wasmaintained from l 10 to 100 atmospheres by feeding in new mixture. Afteran hour, the absorption was almost complete and the autoclave was cooleddown.

The discharge products, analyzed as described in example 1, contained 41mM. of propene, 15.4 mM. of propane, 172 mM. of C, aldehydes, 18.26 mM.of C, alcohols and 1.71 mM. of C, alkyl formates.

Selectively in C, aldehydes 81.3 percent Moles aldehydes/moles alcohols90.4/9.6 Linear products/branched products 89. 1/ 10.9

EXAMPLE 4 2.53 g. (3.66 mM.) 1.785 g. (8.85mM.) 100 cc.

I M kW 4 01]: tri-n-butyl-phosphine NN-dimethyl-ucetarnideC1-l,-C0-N(CH.):

propene 10.56 (251.4 mM.)

After introducing a Hg'CO mixture (1: 1 by volume) until a totalpressure of 68 atmospheres was attained, the autoclave was heated up to180 C. The absorption of gas started at about 162 C. The total pressurewas maintained from 110 to 100 atmospheres by feeding in new mixture.After 34 minutes, the absorption had considerably dropped and theautoclave was cooled down.

The discharged products, analyzed as described in example 1, contained41.3 mM. of propene, 18.9 mM. of propane, 160.8 mM. of C, aldehydes,22.8 mM. of C, alcohols and 1.9 mM. of C, alkyl formates.

Selectivity in C, aldehydes 76.5 percent Moles aldehydes/moles alcohols87.6/ 12.4

Linear products/branched products 89.2/ 10.8

EXAMPLE 5 The following were introduced into a 200 cc. autoclave,operating as described in example 1: )s 4 a)al: tri-n-butyl-phosphinetetrs-methyl-urea propcne 2.53 g. (3.66 mM.) 1.785 g. (8.85 mM.) 100 cc.

10.78 g. (256.6 mM.)

mM. of C, aldehydes, 22.1 mM. of C, alcohols and 3.8 mM. of C, alkylformates.

Selectivity in C, aldehydes 78.4 percent Moles aldehydes/moles alcohols88.8/1 1.2 Linear products/branched roducts 89.5/10.5

EXARIPLE 6 The following were introduced into a 200 cc. autoclave,operating as described in example 1:

[Co(CO)|P(n-C,H|)1l| 2.53 g. (3.66 mM.) 0 2): 1.785 g. (8.83 mM.) CH CNecetonltrile cc.

propene 10.6 g. (252.4 mM.)

After introducing sufficient H,CO mixture 1:1 by volume) to reach atotal pressure of 138 atomspheres, the autoclave was heated to 180 C.The absorption of gas started at about 166 C. The total pressure wasmaintained at from 210 to 200 atmospheres by feeding in new mixture.After 56 minutes, the absorption had considerably dropped and theautoclave was cooled down.

The discharge products, analyzed as described in example 1, contained40.84 mM. of propene, 16.3 mM. of propane, 174.3 mM. of C, aldehydes,12.66 mM. of C, alcohols and 3.5 mM. of formates.

Selectivityin C, aldehydes 82.4 percent Moles/aldehydes alchols 93.2/6.8

Linear products/branched products 87. 1/12.9

EXAMPLE 7 1.262 g. (1.83 mM.) 0.894 g. (4.42 mM.) 50 cc.

5.32 g. (126.7 mM.)

l )s 4 s)s]! tri-n-butylphosphine pmpionitrile CH CH CN propene Afterhaving introduced into the autoclave sufficient H,-C0 mixture 1:1 byvolume) to reach a total pressure of 133 atmospheres, the autoclave washeated up to 178 C. The absorption of gas started at about 158 C. Thetotal pressure was maintained at between 210 and 200 atmospheres byfeeding in new mixture. After 50 minutes, the autoclave was cooled down.The discharge product, analyzed according to the methods described inexample 1, contained: 28 mM. of propene, 7.3 mM. of propane, 79.8 mM. ofC, aldehydes, 6.2 mM. of C, alcohols and mM. mM of formates.

Selectively in C, aldehydes 80.8 percent Moles aldehydes/moles alcohols92.8/7.2

Linear products/branched products 88.4/11.6

Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof and only such limitations should be imposed as areindicated in the appended claims.

We claim:

1. A process for preparing butyric aldehydes by hydroformylation ofpropene in the presence of a cobalt-carbonyl complexed with a phosphine,which comprises carrying out the reaction in a reaction medium selectedfrom the group consisting of N,N-dialkyl-amides of alkanoic acids,tetraalkylureas, and alkyl nitriles, containing from two to 12 carbonatoms, at a temperature of between and 220 C. and at pressures of C0=Hbetween 20 atmospheres'gauge and 400 atmospheres gauge.

2. The process of claim 1, wherein the reaction medium isdimethyl-formamide.

* III i t

2. The process of claim 1, wherein the reaction medium isdimethyl-formamide.